Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1206 | Thousand metric tons | NA |
| 2003 | 1189 | Thousand metric tons | -1.41% |
| 2004 | 1039.39099121094 | Thousand metric tons | -12.58% |
| 2005 | 1005.33001708984 | Thousand metric tons | -3.28% |
| 2006 | 1010 | Thousand metric tons | 0.46% |
| 2007 | 1000 | Thousand metric tons | -0.99% |
| 2008 | 1426 | Thousand metric tons | 42.60% |
| 2009 | 1124 | Thousand metric tons | -21.18% |
| 2010 | 1420 | Thousand metric tons | 26.33% |
| 2011 | 1560 | Thousand metric tons | 9.86% |
| 2012 | 1600 | Thousand metric tons | 2.56% |
